1. Field of the Invention
The invention relates to a method and apparatus for the treatment of waste gases produced in chemical processes. In particular the invention relates to the treatment of waste gases to remove undesirable constituents, such as sulphur dioxide.
2. Description of the Prior Art
It is known to treat waste gases with an alkaline solution, e.g. environmental or surface water such as seawater, in order to remove harmful substances. For example, a method is known in which waste gase is scrubbed with seawater. Seawater is useful in this context because of its natural alkalinity.
In this gas scrubbing method, seawater absorbs sulphur dioxide, and then the sulphite formed is converted by oxidation to sulphate. This process can be carried out in an absorber and a downstream aerator. The used seawater laden with sulphate is then returned into environmental surface water. Examples of such processes using seawater are given in U.S. Pat. No. 4,152,218, GB-A-1356972 and GB-A-1410884. A drawback of this known method is that the returned seawater is also laden with other harmful constituents of the waste gas. In many chemical processes these constituents are produced and load the seawater in such a high concentration that the used seawater cannot be returned to the surface water. As a result of this, the known method has only limited application.